Al^(3+)离子掺杂δ-MnO_(2)的制备和电化学性能

Preparation and Electrochemical Properties of Al^(3+)-Dopedδ-MnO_(2)

采用水热法合成了不同比例Al^(3+)离子掺杂的δ-MnO_(2)纳米粉体.通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、 X射线光电子能谱(XPS)、循环伏安(CV)曲线、电化学阻抗谱(EIS)和恒电流充放电(GCD)曲线等手段对材料的结构和电化学性能进行了表征.结果表明, Al^(3+)离子进入δ-MnO_(2)的晶格替代部分Mn^(3+)和Mn^(4+)离子,使得δ-MnO_(2)电极的性能明显提升.当反应物中Al^(3+)/Mn^(2+)摩尔比为0.45时,所得样品(A0.45M)的性能最好;其在1 A/g电流密度下的比电容为207.61 F/g,是纯相δ-MnO_(2)(A0M)的2.4倍;其在10 A/g电流密度下循环10000次后的比电容为100.81 F/g,容量保持率为81.33%.

Al^(3+)-dopedδ-MnO_(2) nano-powders with different doping ratios were synthesized by hydrothermal method.The influence of Al^(3+)-doping on theδ-MnO_(2) crystal structure and electrochemical performance was characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray photoelectron spectroscopy,cyclic voltammetry,electrochemical impedance spectroscopy and galvanostatic charge-discharge.The results suggested that Al^(3+)ions entered into the crystal lattice ofδ-MnO_(2) to replace some Mn^(3+)and Mn^(4+)ions,which enhanced the electrical conductivity and structural stability ofδ-MnO_(2),and thus significantly improved the electro⁃chemical performance.When the molar ratio of Al^(3+)/Mn^(2+)in the precursor was 0.45,the synthesized product(A0.45M)showed the best electrochemical performance.A0.45M delivered a specific capacitance of 207.61 F/g at a current density of 1 A/g,which was 2.4 times the capacitance of the pureδ-MnO_(2)(A0M).Moreover,A0.45M could maintain a high specific capacitance of 100.81 F/g even after 10000 cycles at 10 A/g,with capacity retention ratio of 81.33%.